Variable throttle valve



Nov. 21, 1950 M, TQWLER ET AL 2,531,371

VARIABLE THROTTLE VALVE Filed March l, 1945 v 2 Sheets-Sheet 1 J. M. TOWLER ETAL 2,531,371

VARIABLE THROTTLE VALVE Nqv. 21, 1950 2 Sheets-Sheet 2 Filed March 1, 1945 FlG.3

Patented Nov. 21, 1950 VAEIQELE EHRGT'ILE VALVE John Maurice Fowler, Thruscross, Summerbridge, near Harrcgate, and Frank Hathorn 'lowler, Dob Iarl-r, near @tley, England, 'assignors to Electraulic Presses'Limited, Rodiey, England Application March 1, 1945, Serial No. 5861416 in Great Britain! 26, 194%5 Section 1, Public Law 690, August 8, 1946 Patent expires January 26, 1965 '7 Claims. (Cl. 137- 144) This invention relates to variable throttle valves for hydraulic systems broadl comprising a variable speed hydraulic motor driven by pressure liquid usually supplied b a pump in which the speed of the motor is controlled by passing the liquid entering or leaving it through a variable throttle valve. Means for maintaining a constant pressure difierence across the said throttle valve may or may not be provided.-

One well known method of constructing such a throttle valve consists in making it in the form of a relatively long passage of Variable length or area. Throttle valves of this type have the advantage that-considerable motion can be imparted to adjust them over their full range, but since the greater part of the pressure loss across them is due to liquid friction, the amount of liquid passing through them at any pressure difference is almostentirely dependent on the viscosity ofthe liquid.

Another well known form of throttle valve consists of a variable orifice, usually controlled by a needle valve, and such a throttle valve, provided the parts are suitably formed, constitutes a variable orifice in which practically the whole of the pressure difference is lost due'to the change of pressure energy into kinetic energy, and with a suitable liquid, such as light oil, the amount passing through such a valve, at a given setting and pressure difierence, is scarcely affected by '4 changes in viscosity. The orifice in such a valve consists of an annular slit and its great disadvantage is that the valve is closed the length of the slit remains substantially constant, but its width decreases, so that long before it is fully closed the width of the slit is so small that the tiniest particles in the liquid are entrapped and the throttle becomes erratic in action. Furthermore, when the valve is nearly, closed, the slit is very narrow and the slightest difference in expansion in the valve due to rises in temperature in the liquid make a considerable difference to the width of the slit.

To overcome this defect a variable throttle valve has been proposed in which the passage for the liquid comprises two slots, one in each of two members which are disposed so that the slots are in parallel alignment when passing liquid, one of said slots being in the form of a narrow slot having a width substantially less than the width of the other slot, variation in the passage thus formed being effected by moving one or both membersrelatively one to the other so as to vary the length of the opening provided by the narrow slot through which the liquid may pass,

In the constructional form in which the above valve has been proposed the narrow slot is formed by cutting an openin of the desired dimensions through the thickness of the wall of a tubular member. However as the valve is required to give a compensated flow control for liquids of varying viscosity it is necessary that the narrow control orifice shall have a sharp edge, be of precise dimensions, and have a wall which is as thin as possible.

By forming the control orifice by cutting a slot through the thickness of a tube itis practically impossible to attain the results set forth above as'for one thing it is very difiiclllt to out a narrow slot of precise axial width in the wall of a tubular member and for another thing the edge of the slot cannot be thin as the wall of the tube has to'be comparatively thick to prevent collapse.

In a variable throttle valve of the present invention we have overcome the above difficulty in a very simple manner which consists in forming the narrow control slot by cutting back the edge of one of two separate but abutting members. In one arrangement the slot is formed by cutting back the edge of a tubular member thus leaving an open gas corresponding in dimensions to the finished dimensions of the slot to be formed and closing the open side of the gap by maintainmg said tubular edge in abutting contact with a flat surface. In another arrangement the slot is formed between two abutting edges one of said edges being on a tubular member and cut back as in the first arrangement.

The desired thin edge of the control slot is formed, in the first arrangement by reducing the thickness of the wall of the tube from the inside for a short distance inwards from one end and in the second arrangement by similarly thinning down both co-acting edges.

Broadly the present invention consists of a variable throttle valve comprisin an inner valve member rotatably mounted within an outer valve.

verse centres of the narrow slot and the wide slot coincide, the effective area of the passage for liquid thus provided by the coinciding slots being varied by partially rotating one valve member relatively to the other valve member to increase or reduce the length of the narrow slot coinciding with the wide slot.

One object of this invention is to provide a throttle valve having a variable orifice and so constructed that the flow of liquid through the valve is not appreciably affected by small changes in the viscosity of the liquid, so that the flow through the valve at a iven pressure is for all practical purposes directly proportionate to the area of the orifice. A further object of the invention is to provide such a valve with means for varying the area of the orifice and so arranged that equal increments in the area of the orifice can be registered on a dial or scale having equal divisions.

A still further object of the invention is to provide such a valve wherein the orifice embodies a narrow slot of constant width, and wherein the walls limiting said narrow slot are made as thin as practicable whereby the flow through the valve is not appreciably affected by small changes in viscosity.

A still further object of the invention is to provide such a valve wherein the variable orifice embodies a narrow slot defined by two cooperating abutting members pressed together to form a fluid tight seal.

A still further obiect of the invention is to provide such a valve wherein the orifice embodies a narrow slot defined by two cooperating abutting members, said members having thin circular edges formed in the mutually abutting portions.

A still further object of the invention is to provide such a valve wherein the orifice embodies a narrow slot defined by cutting back the edge of one of two cooperating abutting members.

In order that the invention may be clearly understood and carried into effect a throttle valve according to the present invention and combined with a reducing valve according to our U. S. Patent No. 2,286,027, will now be described, by way of example.

In the drawings:

Fig. 1 is a longitudinal section through a valve according to the invention.

Fig. 2 is a view at an enlarged scale of a detail of Fig. 1.

Fig. 3 is a longitudinal section of a portion of a valve according to the invention, showing an alternate embodiment thereof.

Fig. 4 is a view at an enlarged scale of a detail of Fig. 3.

Fig. 5 is a cross section of Fig. 2 or of Fig. 4 taken along the line 5-5 looking in the direction of the arrows.

The variable throttle valve illustrated in the drawing comprises an inner valve member I, rotatably mounted in an outer valve member 2 which in turn is mounted in a valve body 3. The inner valve member consists of a tube, which is closed at the outer end which projects from the valve as at 4, and it is also closed at the inner end by a cylindrical pad 5, the fiat face of the pad being held against the end of the tube by a light spring 6. The inner member and the pad are a lap fit in the bore of the outer member, so as to prevent any appreciable leakage axially. The inner end of the tube is reduced to a thin edge of less than one sixteenth of an inch thick and this edge is cut back axially about fifteen thousandths of an inch for a quarter of its peripheral length, so that when the valve is assembled with the pad closing the end of the. tub

' 2, which is a view of the abutting portions of said inner valve member I and said pad 5. The outer valve member 2 is provided with a wide transverse slot 8 extending to nearl half the circumference of the valve bore and when the valve is assembled, the narrow slot 1 formed by the inner member and pad, is located on the transverse centre line of the wide slot 8 in the outer member, which is surrounded by an annular chamber 9 in the valve body to which pressure liquid is delivered from the valve inlet [0. The

outer end of the inner valve member is provided with radial holes I I connecting the bore I 2 of the tube with another annular chamber l3 in the valve body which is connected to the valve outlet M. The inner valve member is provided with a knurled knob l5 by which it may be rotated, so as to increase or reduce the effective length of the slot 1 and a circular dial is graduated in equal divisions is provided to register equal increments in the area of the orifice. When the valve is in operation, pressure liquid passes from the valve inlet through the wide slot 8 and thence through the narrow slot 1 into the bore IQ of the inner member and thence through the radial holes I! to the valve outlet Hi. The valve is so constructed that the inlet pressure has access to a space I Tat the rear of the circular pad 5 which closes the bore of the outer member, thereby holding the pad against the end of the tubular member by hydraulic pressure in addition to the light spring 6.

The delivery of pressure liquid to the annular chamber 9 is controlled by an automatically operating reducing valve of the kind accordin to our U. S. Patent No. 2,286,027. This reducing valve comprises a valve plunger l8 mounted to slide within a cylindrical bore l9 formed by a tubular member 20 which in turn is a tight fit within an outer member 2|. Surrounding this outer member 2! is an annular chamber 22 to which pressure liquid has access through a main inlet opening, not shown.

The liquid in the chamber 22 is permitted to flow into the annular chamber 9 when the valve plunger I8 is in the position shown by means consisting of longitudinally spaced sets of radial holes 23, 32 in the wall of the tubular member 20, coinciding annular grooves 24, 25 in the plunger body, a longitudinal passage 26 within the plunger and radial holes 21 connecting the grooves 24, 25 with the longitudinal passage 26. The plunger I8 is held in the open position shown by a spring 28 against the opposing hydraulic pressure within the space I1. When this pressure rises sufiiciently to overcome the pressure of the spring the plunger will be moved to the right to reduce or cut off the flow of liquid from the main inlet to the annular chamber 9 serving the variable throttle valve of the present invention.

.The plunger l8 of the reducing valve is maintained in hydraulic balance laterally by the annular grooves 24, 25 and the space 29 at the outer end of the plunger is open to the pressure within the bore l2 by connecting said space to the outlet M of the throttle valve by passage 30, 3|.

..Yet a further embodiment of this invention shown in Figures 3, 4 and 5 consists of a variable i t e al constructed as described in. the

previous embodiment, excepting that the face of the circular pad which abuts against the end of the tubular inner member is cup shaped and provided with a thin edge or rim 33 corresponding to the thin edge of the tubular inner member against which it abuts. This construction ensures that the walls on both sides of the slot are as thin as possible, so that the flow through the valve is not appreciably aiiected by small changes of viscosity.

Inasmuch as all parts of the embodiment shown in Figs. 3 and 4 are identical with the corresponding parts of the embodiment shown in Fig. 1 with the exception of the modification above set forth in the configuration of the pad 5, the same numerals used in Fig. l have been used in Figs. 3 and 4- to designate corresponding unchanged parts. Fig. 5 can be interpreted as illustrating either the embodiment of Fig. 1 or the embodiment of Figs. 8 and 4, because it shows the inner valve member I which is identical in both embodiments.

What we claim is:

l. A variable throttle valve for hydraulic systems, comprising an outer valve member, an inner valve member relatively rotatable within said outer valve meirber and consisting of a tube having an outlet and an open end, said end having its wall thickness reduced interiorly for a portion of its peripheral length to form a thin arcuate edge, an abutment member opposing said open end and having therewith a fluid tight sealing contact, a shallow transverse notch formed in said thin arcuate edge to define a narrow transverse slot between said abutment member and said thin arcuate edge, and a wide transverse slot in the wall of said outer valve member for a portion of its peripheral length and so situated therein that the full width of said narrow slot will register transversely with said wide slot upon endwise movement of said slots into communication, an effective area for the passage of liquid being provided by register-- ing portions of said two slots, said effective area being controllable by partially rotating one of said valve members relatively to the other to vary the effective len th of said registering portions of said two slots.

2. A variable throttle valve for hydraulic systems, comprising an outer valve me ber, an inner valve member relatively rotatable within said outer valve member and consisting of a tube having an outlet and an open end, said end having its wall thickness reduced interiorly to form a thin circular edge, an abutment member opposing said thin circular edge, means for pressing said abutment member a ainst said thin circular edge to effect a fluid tight sealing contact therebetween, a narrow transverse slot in said inner valve member between said abutment member and said thin circular edge out back in the latter along a portion of its peripheral length, and a wide transverse slot in the wall of said outer valve member for a portion of its peripheral length and So situated therein that the full width of said narrow slot is in registration with said wide slot axially of said valve members, an effective area for the passage of liquid being provided by registering portions of said two slots,

effective area being controllable by partially rotating one of said valve members relatively to the other to vary the effective length of said registering portions of said two slots.

3. A variable throttle valve for hydraulic systems, comprising an outer valve member, an innet valve member consisting of a tube rotatable in said outer valve member and having an open end, said end having its wall thickness reduced interiorly to form a thin edge, a member embodying a rim having a thickness of the same order as the thickness of said thin edge, said rim abut-ting said thin edge and forming therewith along the area of abutment a fluid tight seal, a narrow transverse slot formed in said inner valve member for a portion of its peripheral length between said rim and said thin edge, said thin edge extending circumferentially of the tube through the :full arcuate length of said narrow slot, and a wide transverse slot in the wall of said outer valve member for a portion of its peripheral length and so situated therein that the full width of said narrow slot is in registration with said wide .slot axially of said valve members, said valve members respectively having inlet and outlet passages opening respectively to and from said slots, an efiec-tive area for the passage of liquid being provided by registering portions of said two slots, said .efiective area being control'lable by partially rotating said narrow slot with respect to said wide slot to vary the effective length of said registering portions thereof.

4. A variable throttle valve for hydraulic sys-- tems, comprising an outer valve member, an inner valve member relatively rotatable within said outer valve member and consisting of a tube having an outlet and an open end, said end having its wall thickness reduced interiorly to form a thin circular edge, a member embodying a rim which abuts said thin circular edge and has a thickness of the same order as the thickness of said thin circular edge, said thickness eing as small as practicable, mean for pressing said rim against said thin circular edge to form a fluid tight seal therebetween along the area of abutment, a narrow transverse slot between said rim and said thin circular edge cut back in the latter along a portion of its peripheral length, a wide slot in the wall of said outer valve member for a portion of its peripheral length and so situated therein that the full width of said narrow slot will register transversely with said wide slot upon endwise movement of said slots into communication, an effective area for the passage of liquid being provided by registering portions of said two slots, said effective area being'controllable by partially rotating one of said valve members relatively to the other to vary the efiective length of said registering portions of said two slots, said narrow slot being completely defined by walls so thin that the passage of liquid through said effective area is not appreciably affected by small changes in the viscos ity of the liquid.

5. A variable throttle valve for hydraulic systems, comprising an outer valve member, an inner valve member relatively rotatable within said outer valve member and consisting of a tube having an outlet and an open end, said end having its thickness reduced interiorly to form a thin edge, an abutment member having a flat surface opposing said thin edge, resilient means for pressing said abutment member against said thin edge to form a fluid type seal therebetween along the area of abutment, a narrow transverse slot between said member and said thin edge out back in the latter along a portion of its peripheral length, said thin edge extending circumferentially of the tube through the full arcuate length of said narrow slot, and a wide transverse slot in the wall of said outer valve member for a portion of its peripheral length and so situated therein that the full width of said narrow slot will register with said wide slot upon endwise movement of said slots into communication, an efiective area for the passage of liquid being provided by registering portions of said two slots, said efiective area being controllable by partially rotating one of said valve members relatively to the other to vary the effective length of said registering portions of said two slots.

6. A variable throttle valve for hydraulic systems, comprising an outer valve member, an inner valve member consisting of a tube rotatable in said outer valve member and having an open end, said end having its wall thickness reduced interiorly to form a thin circular edge, an abutment member opposing said thin circular edge and forming therewith a fluid tight seal along the area of contact, a narrow transverse slot formed in said inner valve member for a portion of its peripheral length between said abutment member and said thin circular edge, a wide transverse slot in the wall of said outer valve member for a portion of its peripheral length and so situated therein that the transverse centres of said two slots coincide, said valve members respectively having inlet and outlet passages opening respectively to and from said slots, an effective area for the passage of liquid being provided by registering portions of said two slots, means for controlling said effective area by partially rotating said narrow slot with respect to said wide slot to vary the eifective length of said registering portions thereof, and a scale operatively connected to said means and controlled thereby for indicating the variations of said effective area.

'7. A variable throttle valve for hydraulic systems, comprising an outer valve member, an inner valve member relatively rotatable Within said outer valve member and consisting of a tube having an outlet and an open end, said end having its wall thickness reduced interiorly to form a thin circular edge, an abutment member opposing said thn circular edge, means for pressing said abutment member against said thin circular edge to form a fluid tight seal therebetween along the area of abutment, a narrow transverse slot between said abutment member and said thin circular edge out back in the latter along a portion of its peripheral length, a wide transverse slot in the wall of said outer valve member for a portion of its peripheral length and so situated therein that the transverse centres of said two slots coincide, an effective area for the passage of liquid being provided by registering portions of said two slots, means for partially rotating one of said valve members relatively to the other to control said efiective area by varying the effective length of said registering portions of said two slots, and a scale operatively connected to said means and having equal divisions to indicate equal increments in said effective area.

JOHN MAURICE TOWLER.

FRANK HATHORN TOWLER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,397,867 Jones Nov. 22, 1921 2,158,737 Wunsch May 16, 1939 2,343,375 Herman Mar. 7, 1944 Certificate of Correction Patent No. 2,531,371 November 21, 1950 JOHN MAURICE TOWLER ET AL. It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 1, line 33, after the Word that insert as; column 2, line 27, for gas read gap; column 6, line 37, for mean read means; line 68, for type read tight;

and that the said Letters Patent should he read as corrected above, so that the same may conform to the record of the case in the Patent Oflice. Signed and sealed this 30th day of January, A. D. 1951,

THOMAS F. MURPHY,

Assistant Oommiss'z'oner of Patents 

